"Even while our hardcover sales continue to grow, the Kindle format has now overtaken the hardcover format," said Jeff Bezos, founder and CEO of Amazon.com. “Amazon.com customers now purchase more Kindle books than hardcover books.”

In December and January, industry watchers took note of the fact that Amazon.com's bestseller list was full of free books; in May, the company split the list into "Top 100 Paid" and "Top 100 Free." Today's figures exclude free books for the Kindle.

However, Amazon.com continues to emphasize the price differential. Its press release points out that of 630,000 not-free ebooks available for the Kindle, "Over 510,000 of these books are $9.99 or less."

The point about the low price of ebooks for the Kindle is an important one; publishers and Amazon have tussled over how much those books should cost. Once Apple's iPad and its iBook store came on the scene, it presented an alternative pricing model -- and alternative prices of $12 or $15 for an ebook. Amazon.com is sending a message to publishers that its lower-priced ebooks are finding a place with buyers.

It's impressive that Charlaine Harris (author of the Sookie Stackhouse mysteries, the basis of the television series "True Blood"), Stephenie "Twilight" Meyer, James Patterson (author of the Alex Cross series and others), romance maven Nora Roberts and Stieg "The Girl With the Dragon Tattoo" Larsson have each sold 500,000 books for the Kindle.

But what isn't being said is that these aren't necessarily new books; most of these authors have an impressive backlist. James Patterson has published almost 40 novels; Nora Roberts' books have been issued and reissued so frequently that it's almost impossible to tally her published work. Stieg Larsson, who died in 2004, is the underachiever: His popular mystery series consists of only three books.

When CDs began to outpace vinyl, music companies realized that they could sell the same original works to fans a second time, in a new format. How much of Amazon.com's Kindle sales are an echo of this -- readers purchasing much-loved favorites in a new format -- is impossible to say without seeing sales figures based on specific titles. And that's something that no companies, neither publishers nor Amazon.com, seems interested in releasing.

Once, the word ebook was all but equivalent with a book sold for the Kindle. Amazon.com may be a huge part of the ebook picture, but now it has to share the stage with other players.

Evidence of this new landscape was clear in the release. In it, Bezos said, "The growth rate of Kindle device unit sales has tripled since we lowered the price from $259 to $189." Amazon.com's cheapest Kindle is now $300 less than the iPad, and its price is almost the same as Barnes & Noble's Nook (Kindle is $10 less) the Sony Reader ($20 cheaper than the Kindle) and Borders' Kobo ($30 cheaper than the Kindle). The Kindle price drop has apparently appealed to readers -- its sales are going up -- but with an increasingly crowded market, will it continue to maintain dominance? How much does the price drop affect the company's ability to profit from those sales?

The Amazon.com release indicates good news for ebooks overall. Whether it means that Amazon.com has cornered the ebook market is a question for another day.

Photo: Charlaine Harris at the premiere of "True Blood" season 3 at the Arclight Theater in Hollywood, June 8, 2010. Credit: Michael Buckner/Getty Images

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